1. Field of the Invention
The present invention relates to the routing of Internet Protocol (IP) traffic using optical burst switching and more particularly the present invention relates to selecting the offset between a control packet and a data burst to optimize the network performance.
2. Description of the Related Art
Rapid growth in the volume of Internet traffic over the last decade has generated a considerable amount of interest in devising new high-speed transmission and switching technologies. Wavelength division multiplexing can support a number of simultaneous high-speed channels on a single optical fiber and can thereby provide an enormous bandwidth at the physical layer. In order to exploit this bandwidth to meet the future traffic requirements, higher layer communication protocols must be developed to make efficient use of the transmission capacity of such optical fiber arrangements.
Presently, wavelength division multiplexing deployment comes in two varieties, namely, wavelength routing and SONET/SDH framing on wavelengths. In wavelength routing, a complete wavelength (or a sequence of wavelength segments joined by wavelength converters is assigned to a communication path between the two end-points. Such wavelength paths are preconfigured, and there is no need for optics-electronics-optics conversion at the intermediate nodes. However, such a provisioning of a complete wavelength tends to be inefficient when there is not enough traffic between the two end-points or when the traffic between them is bursty. In SONET/SDH framing on wavelengths, a time slot structure is created on the wavelength. An end-to-end communication path is established by assigning time slots on wavelengths of successive hops. The intermediate nodes extract/insert data into appropriate time slots. In this approach, the intermediate nodes have to perform optics-electronics-optics conversion for extracting/inserting data (also called multiplexing) into time slots. Since the operating speed of electronic devices is considerably slower than the transmission speed provided by the optical wavelength division multiplexing, the optic-electronics-optic conversion at the intermediate nodes in the data path should be eliminated.
Ideally, an all-optical packet eliminates the electronics entirely, thus removing the speed bottleneck as well as overcoming the shortcomings of the wavelength routing approach. In an all-optical packet switch, the data packets arriving on an incoming optical fiber are switched to an outgoing fiber in an entirely optical domain.
As a presently implementable alternative to all-optical packet switches, optical burst switching still allows the switching of data bursts in the optical domain by performing resource allocation in the electronic domain. In optical burst switching, a control packet precedes every data burst and the control packet and the corresponding data burst are launched at the source at points in time separated by an offset. The offset is determined at the time that the control packet is launched at the source. The control packet includes information required to route the data burst through the network and also includes the length of the corresponding data burst and its offset value. The control packet is processed electronically at each of the intermediate nodes for making routing decisions and the switching fabric at each node is configured accordingly to switch to the data burst that is expected to arrive after a time interval corresponding to the offset field of the control packet. Thus, the data burst is entirely optically switched to eliminate the electronic bottleneck.